[ RadSafe ] Radon Travel in Granite

dckosloff at firstenergycorp.com dckosloff at firstenergycorp.com
Thu Jul 31 07:50:25 CDT 2008

Hi Kai ( I like the sound of that, but I am probably pronouncing it wrong),
Al and all,

This seems to be related to any discussion of the radioactivity from

"Radiation Sources at the U.S. Capitol and Library of Congress Buildings"

Unfortunately, I don't have any granite counter tops.  How about marble
window ledges?

Don Kosloff, License Renewalist
6310 N. Harris Harbor Drive
Oak Harbor OH 43449

             "Kai Kaletsch"                                                
             <eic at shaw.ca>                                                 
             Sent by:                                                   To 
             radsafe-bounces at r         "al gerhart"                        
             adlab.nl                  <webmaster at solidsurfacealliance.org 
                                       >, <radsafe at radlab.nl>              
             07/30/2008 09:51                                              
             PM                                                    Subject 
                                       Re: [ RadSafe ] Radon Travel in     

Hi Al and all,

Aside from any incremental increase in radon or gamma exposure (which I
don't tend to get too excited about), 0.25% U ore would NOT be my first
choice of food preparation surface. If those numbers are correct, then it
important that a sample of the same material be made available for testing
by the other stake holders in this (by now somewhat politicized) issue.

0.25% U is quite high and, at least in Canada, there are several
dealing with radioactive materials that kick in at much lower levels. For
example, 0.05% U (5 times lower than your rock) is considered 'source
material' and is a 'controlled nuclear substance' (even if it is contained
in a granite countertop) and a license is required to export the material
from Canada. So, if your slab of granite came from Canada, and the exporter

didn't approach our nuclear regulator to get a license ... You can see our
Nuclear Non-proliferation Import and Export Control Regulations here:

Before, you asked if there is a quick and dirty way of getting from cpm or
mR/Hr to ppm. You can get in the right ballpark if you take readings on a
bunch of  normal granite, average the readings, assume that corresponds to
Dan's value of ~ 10 ppm and scale the result of your sample.

You can also calculate a dose rate for a given geometry as a function of
uranium content. I have a program on my website that does this (see
http://members.shaw.ca/eic/Tools/JavaShield/Index.html , read the
documentation and use the rectangular source geometry). If you are using a
pancake probe, these are not energy compensated and your reading will be
by a bit. More importantly, make sure you put ~ 1 mm sheet of aluminum (or
similar) between the source and the pancake. Otherwise, your detector will
see alpha and beta radiation and your mR/Hr reading will be meaningless
want to see gamma). That is probably how you got your 10.5 mR/Hr reading,
which is too high, even for 0.25%U.


Kai Kaletsch
Environmental Instruments Canada Inc

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